1. Field of the Invention
The present invention relates to a device for automatically controlling flow of exhaust air to a ventilated rack for animal cages.
2. Related Art
Systems for providing air and removing exhaust from racks containing animal cages are known. U.S. Pat. No. 5,307,757 describes a ventilated animal rack and animal cage system including a forced air system in which positive air is supplied by an air inlet manifold. Air is removed from the cage by negative air pressure to an exhaust manifold. The exhausted air is treated with a laboratory air treatment system or portable HEPA filtered exhaust unit and is released to the atmosphere.
Alternatively, exhaust for a rack of animal cages is removed by a central exhaust system. Several racks can be connected to the exhaust system. One end of an exhaust drop is connected to a duct of the exhaust system for removing exhaust. The other end of the drop is connected to an exhaust plenum of the rack of animal cages. The exhaust operates by negative pressure. Air is supplied to the ventilated rack with a rack mounted supply blower. This system has the disadvantage that if the supply blower malfunctions or is turned off outside air will be drawn into the rack and cages by the exhaust system. Accordingly, the cages can be contaminated with outside air.
Conventional control valves are used to control laboratory air flow of fume hoods having general exhaust and room supply air. The valves regulate air flow as duct static pressure varies. A pressure independent controller within the control valve adjusts to static pressure. For example, the controller can include a cone biased in a venturi to maintain a set flow. An example of this type of control valve is manufactured as an Accell(copyright)II Airflow Control Valve, by Phoenix Controls Corporation, Massachusetts. This type valve has the shortcoming of using a complicated mechanical system, which is expensive to manufacture and can be subject to mechanical failures.
It is desirable to provide a device for automatically controlling exhaust flow to a ventilated rack of animal cages upon the condition of failure or interruption of an air supply blower which provides air to the ventilated rack, thereby assuring a barrier condition of the ventilated rack and preventing imbalance of the compromised rack with other ventilated racks connected to a central exhaust system.
The present invention relates to a device for automatically controlling exhaust flow to a ventilated rack of animal cages when an air inlet system, such as an air supply blower, to the rack is not operating. Accordingly, the device assures that the exhaust system is balanced when air supply to the ventilated rack is compromised. The device creates a partial obstruction to air flow in the exhaust connection, thereby preventing flow of exhaust to the rack and assuring a barrier condition of the rack.
The device includes a damper housing that is adapted to be connected between an exhaust outlet of the ventilated rack and an exhaust system. A movable damper is positioned within the damper housing. A linear actuator is activated to move the damper into an open position when the air inlet system is fully operating. The damper reverts to a partially closed position when a failure of the air inlet system is detected.
An air inlet interface internal in the air inlet system detect the operating condition of the air inlet system. The air inlet interface provides a signal indicating that the air inlet system is operating and proper air supply is provided to the rack. When the air inlet interface detects an alarm condition, such as a loaded filter, power failure or blower malfunction, the air inlet interface provides a signal indicating that the air inlet system is not operating. An auto damper interface receives the signals for the air inlet interface. The auto damper interface provides an electrical connection to the linear actuator upon receiving the signal indicating that the air inlet system is operating for moving the damper into an open position. The auto damper interface deactivates the linear actuator upon not receiving the signal indicating that the air inlet system is operating and thus moves the damper into a partially closed position.
The invention will be more fully described by reference to the following drawings.